Abstract. Skin structure is studied in a broad sample of frog species of the genus Telmatobius and its relatives. These frogs exhibit different ecological habits and occupy different habitats. The results demonstrate that the coexistence of two types of serous glands, a rare feature among anurans, is widespread in Telmatobius. These types of serous glands, called Types I and II, are characterized by different sizes of their granules. However, some strictly aquatic species of the genus have only one type of serous glands (Type I); this feature might be interpreted, within Telmatobius, as the result of independent losses of serous glands of Type II. Another finding was the occurrence of the Eberth-Kastschenko (EK) layer in the dermis of almost all studied species of Telmatobius. This result was unexpected, because the EK layer is generally absent in aquatic anurans and was thought of as absent in Telmatobius. However, there are differences in its thickness that, combined with data of ecological habits and main habitats, reveal a complex pattern within Telmatobius, as well as within and between the other studied genera. Although we are far from understanding the significance of the presence of two types of serous glands in Telmatobius or the functions of the EK layer in general, these taxonomic and ecologic patterns could guide future research.Key words. Skin glands, serous glands, Eberth-Kastschenko layer, calcified layer, aquatic frogs, semiaquatic frogs, terrestrial frogs, Andes.